textproduct: Quad Cities

KEY MESSAGES

- There is a Slight/Marginal (level 1+2 out of 5) risk for severe weather tonight. Primary threats will be damaging wind and heavy rain. - There is an Enhanced/Slight (level 2+3 out of 5) risk for severe weather Monday. All hazards will be possible.

- Breezy and cooler Tuesday, with dry conditions expected through at least Thursday.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 215 PM CDT Sun May 17 2026

A shortwave evident on water vapor over eastern MN aided by strong upper level divergence and a 35kt LLJ allowed for some scattered thunderstorms to develop over northeast IA and northwest IL this morning. Elsewhere light showers occurred for some and has now diminished. A persistent deck of stratus stretching from north central IA towards southwest WI kept our far northwest counties a little cooler today. A warm front extended from southwest WI, towards Waterloo and westward along the Hwy 20 corridor. Another subtle outflow boundary was seen over central IA just north of DSM, where low clouds were observed.

Breezy south winds and humid conditions will continue this afternoon and evening, with the 18z DVN sounding already sampling 33kts at top of mixed layer (880mb). An increasing LLJ ahead of main surface low, may allow some scattered showers to develop over northern IA this evening, but should stay west of the local area. Attention then turns to storm evolution out in the Plains.

Tonight...latest 12z CAMs and REFS solutions suggest this MCS to remain to our west until after midnight tonight and then track east-southeast through the CWA. Current thinking is similar to previous shift where this activity moves through in a decaying mode through sunrise, since CAPE/shear overlap quickly diverges overnight. Wouldn't be surprised if two lines of storms occur with one following the CAPE gradient to the south, and another staying just to our north where better kinematics will be located. Nonetheless, cold pool propagation mechanics to still support a damaging wind threat as storms enter our northwest CWA tonight. High PWs will also bring a heavy rain threat, with 12z HREF 3-hr PMM values over 1.5" in spots tonight. Progressive nature of storms should limit flash flood potential at least for tonight.

Monday...lingering showers and thunderstorms will be seen through the morning (perhaps an MCV?) that may keep severe risk around until mid-day. How quickly the atmosphere recovers will be key to how soon we see convection later in the day. A dry period is anticipated late morning/early afternoon, with strong southerly flow allowing for airmass recovery and building instability. There is high confidence that CI will occur well to the west of the CWA, with initial cells capable of very large hail and strong tornadoes. However, how long semi-discrete cells maintain until becoming more linear is still uncertain and there is still quite the variance in the timing and evolution of storms that will hopefully be ironed out in the next 12-18 hours. The general consensus is for another late evening/overnight show locally with a messy storm mode (multicells-squall line?) moving through west to east with severe winds/embedded mesovorts becoming the primary threats. Heavy rain will become more a concern with this round depending on who receives rain tonight, with some localized areas very well could end up receiving 3+ inches of rain! This is suggested by the 12z HREF 48-hr PMM generally along and south of I-80. WPC has a slight risk for excessive rainfall for the entire area and will need to be monitored for further messaging in later forecasts.

LONG TERM /TUESDAY THROUGH SUNDAY/

Issued at 215 PM CDT Sun May 17 2026

Tuesday...cold front to push through the area in the morning, with precip chances quickly exiting to the east and southeast. Some breezy northwest winds may occur for a few hours behind the front, ushering in cooler and drier air. Some isolated CAA showers may develop in the afternoon east of MS RVR, but will quickly exit out of the area. Afternoon highs to top out in the mid 60s near Waterloo, to near 80 degrees near Peoria.

Wednesday through Saturday...The latest ensembles suggest high pressure regime to shunt the main storm track to the south of the region for mush of the mid to late week period. Cooler temps in the 60s moderating back to the 70s by Friday. The next main chance for precip may not come until Friday if the latest wave-handling by the ensembles is correct.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 605 PM CDT Sun May 17 2026

An active stretch of weather will be seen through tonight. Between 05-10Z, we will see a decaying line of strong to severe storms pass through the area roughly from west to east. As this passes through, we can expect strong winds from the thunderstorms, where we currently mention 40 KT gusts possible. Although, if storms remain strong to severe, some stronger gusts cannot be ruled out. Confidence is lower on that at this point. Along with the strong winds, we will see frequent lightning and heavy rainfall, which may result in brief cig/vis reductions into MVFR. The strongest storms will be along the leading edge, decreasing in intensity an hour or two after they pass. Behind the main line of storms, showers and infrequent lightning will continue, with the strong/severe gust potential significantly decreasing. We can continue to see showers/storms in repeated rounds at MLI/BRL into Monday AM, some of which may be strong to severe, leaving the area between 12-15z. Otherwise, winds ahead of and beyond the passing line of storms will remain gusty and out of the south, with gusts upwards to 25-30 KTs possible at times.

We will have a brief period of LLWS tonight ahead of the passing line of storms, generally around 40-45 KTs out of the south- southwest. These conditions will deplete as the storms pass through.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.